CN111884515A - Current detection method and device of LLC resonant converter - Google Patents

Current detection method and device of LLC resonant converter Download PDF

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Publication number
CN111884515A
CN111884515A CN202010699920.2A CN202010699920A CN111884515A CN 111884515 A CN111884515 A CN 111884515A CN 202010699920 A CN202010699920 A CN 202010699920A CN 111884515 A CN111884515 A CN 111884515A
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current
resonant converter
llc resonant
period
llc
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CN111884515B (en
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刘洋
王伟康
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Hubei Yukong Zhiqu Technology Co ltd
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Huazhong University of Science and Technology
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Priority to EP21845927.9A priority patent/EP4012911A4/en
Priority to PCT/CN2021/072339 priority patent/WO2022016835A1/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/01—Resonant DC/DC converters

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a current detection method and a device of an LLC resonant converter, belonging to the technical field of power electronic switching power supplies and comprising the following steps: after the resonant current of the LLC resonant converter is decomposed into a form of superposition of sine component and cosine component, the output current of the LLC resonant converter is arranged into an expression i of the resonant current and the exciting current of the LLC resonant converterd(t); in the operation process of the LLC resonant converter, sampling output current at any time t 'within a half resonant period for one time to obtain the relation between resonant current and exciting current at the time t', simultaneously establishing the relation, solving the relation that the resonant current and the exciting current are equal at the starting time of the half resonant period to obtain the amplitude of two components of the resonant current, substituting the amplitude into an expression idAnd (t), obtaining a waveform expression of the output current of the LLC resonant converter in one switching period. The invention can realize the real implementation of the current of the LLC resonant converterAnd the time and accuracy detection is realized, and the dynamic performance of a subsequent control algorithm is improved.

Description

Current detection method and device of LLC resonant converter
Technical Field
The invention belongs to the technical field of power electronic switching power supplies, and particularly relates to a current detection method and device of an LLC resonant converter.
Background
In order to comply with the trend of miniaturization of switching power supplies, the power semiconductor device has been selected to have a higher frequency, because the most effective way to reduce the size and increase the power density of the switching power supply is to increase the switching frequency. In recent years, third generation wide bandgap semiconductors have been widely used in the field of switching power supplies because of their excellent characteristics such as high switching frequency and low driving loss, which can greatly improve the performance of power supply devices. The LLC resonant converter using the third generation semiconductor is a hot point of research because the LLC resonant converter can realize soft switching in the full load range to reduce the switching loss, has a simple and efficient structure, and is very well matched with the characteristics of the third generation semiconductor.
Accurate and fast current feedback information is required for accurate closed-loop control of a single-phase LLC resonant converter and accurate current sharing control of a multi-phase LLC resonant converter. With the application and popularization of the third generation semiconductor, the switching frequency of the LLC resonant converter is improved to hundreds of kHz and even MHz level, the output current waveform of a rectifying circuit at the secondary side of the transformer is a half-wave waveform of 2 times of the switching frequency when the LLC resonant converter works, and the amplitude of the current ripple is very large. Due to the ultrahigh switching frequency and the characteristics of the LLC, accurate real-time output current information of the LLC resonant converter is difficult to obtain by a common current detection method, namely the instantaneous load of the LLC resonant converter is difficult to know, and challenges are brought to accurate control of the LLC resonant converter under high-frequency work and current-sharing control of the interleaved parallel LLC resonant converter.
Before the third generation semiconductor is popularized and applied, the switching frequency of the LLC resonant converter is generally low, and in order to obtain current information during the operation of the converter, the converter is generally subjected to high-frequency current sampling 5-10 times per cycle so as to estimate the current waveform per cycle; in the situation that the real-time requirement on the current information is not high, low-pass filtering sampling can be carried out on high-frequency half-wave current through a low-pass filtering circuit, and the actual waveform is estimated through the sampled low-pass current value.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a current detection method and a current detection device of an LLC resonant converter, and aims to solve the technical problem that the current information of the LLC resonant converter cannot be accurately acquired in real time by the existing high-frequency LLC resonant converter current detection method.
To achieve the above object, according to an aspect of the present invention, there is provided a current detection method of an LLC resonant converter, comprising:
converting the resonant current i of an LLC resonant converterrDecomposing the output current i of the LLC resonant converter into a form of superposition of a sine component and a cosine componentdArranged as resonant current i of LLC resonant converterrAnd an excitation current imIs expressed by the expression id(t)；
During the operation of the LLC resonant converter, the output current i is optionally adjusted at a time t' within one half resonant perioddSampling for one time to obtain a sampling current value id(t'), thereby obtaining a resonance current i at time trAnd an excitation current imThe relationship of (1);
at the beginning of a half resonance period in parallel, the resonance current irAnd an excitation current imEqual relation, and at time t', the resonant current irAnd an excitation current imTo obtain a resonant current i by solvingrSubstituting the amplitudes of the sine component and the cosine component into the expression id(t) obtaining an output current i of the LLC resonant converterdAnd (3) a waveform expression in a switching period of which the half resonant period belongs.
The invention uses the resonant current i of the LLC resonant converterrDecomposed into a form of superposition of sine component and cosine component, so that the resonant current irThe expression of (a) only contains two unknowns of sine component amplitude and cosine component amplitude; will output a current idArranged as resonant current i of LLC resonant converterrAnd an excitation current imIs expressed by the expression idAfter (t), due to the excitation current imOnly with respect to known parameters of the structure and output voltage of the LLC resonant converter, the expression idThere are also only two unknowns in (t); since at the beginning of a half resonance period the resonance current irAnd an excitation current imThere is an equality relationship, only for the output current idSampling once to obtain resonant current irAnd an excitation current imThe relation between the two voltage and the output current i at another moment is obtained by combining the two relational expressionsd(t) waveform expressions over respective switching periods; the method does not need to sample for many times and complex fitting process in the process of detecting the current of the LLC resonant converter, can realize real-time and accurate detection of the current, and improves the dynamic performance of a subsequent control algorithm.
Further, the output current i of the LLC resonant converterdArranged as resonant current i of LLC resonant converterrAnd an excitation current imIs expressed by the expression idAfter (t), expression id(t) is:
id(t)＝N|ir(t)-im(t)|
wherein, N represents the turn ratio of the primary side and the secondary side of the transformer in the LLC resonant converter, and t represents a time variable.
In some alternative embodiments, for the output current idThe half resonant period of sampling is the first half resonant period within one switching period.
Further, the resonant current i of the LLC resonant converterrAfter being decomposed into a form of superposition of sine component and cosine component, the resonant current irThe expression of (a) is:
Figure BDA0002592637710000031
wherein, Ir1And Ir3Respectively representing the amplitudes, t, of the sine and cosine components of the decomposed resonant currentrRepresenting the resonance period of the LLC resonant converter and t representing a time variable.
Further, exciting current i of LLC resonant convertermThe expression of (a) is:
Figure BDA0002592637710000032
wherein N represents the turns ratio of the primary side to the secondary side of the transformer in the LLC resonant converter, VoRepresenting the output voltage, t, of the LLC resonant converterrRepresenting the resonance period, L, of the LLC resonant convertermThe transformer magnetizing inductance in the LLC resonant transformation is shown, and t represents a time variable.
In some alternative embodiments, for the output current idThe half resonance period for sampling is the second half resonance period within one switching period.
Further, the resonant current i of the LLC resonant converterrAfter being decomposed into a form of superposition of sine component and cosine component, the resonant current irThe expression of (a) is:
Figure BDA0002592637710000041
wherein, Ir1And Ir2Respectively representing the amplitudes, t, of the sine and cosine components of the decomposed resonant currentrRepresenting the resonance period of the LLC resonant converter and t representing a time variable.
Further, exciting current i of LLC resonant convertermThe expression of (a) is:
Figure BDA0002592637710000042
wherein N represents the turns ratio of the primary side to the secondary side of the transformer in the LLC resonant converter, VoRepresenting the output voltage, t, of the LLC resonant converterrRepresenting the resonance period, L, of the LLC resonant convertermThe transformer magnetizing inductance in the LLC resonant transformation is shown, and t represents a time variable.
Further, the current detection method of the LLC resonant converter provided by the present invention further includes:
output current i of LLC resonant converterdCalculating the output current i according to the waveform expression in the switching period of the half resonant perioddPeak and/or significant values within the corresponding switching period.
According to another aspect of the present invention, there is provided a current detection apparatus of an LLC resonant converter, comprising: a sampling unit and a calculating unit;
a calculation unit for calculating the resonant current i of the LLC resonant converterrDecomposing the output current i of the LLC resonant converter into a form of superposition of a sine component and a cosine componentdArranged as resonant current i of LLC resonant converterrAnd an excitation current imIs expressed by the expression id(t)；
A sampling unit for selecting an optional time t' in a half resonance period to output current i during the operation of the LLC resonant converterdSampling for one time to obtain a sampling current value id(t'), thereby obtaining a resonance current i at time trAnd an excitation current imThe relationship of (1);
a calculation unit for simultaneously calculating the resonance current i at the start of a half resonance periodrAnd an excitation current imEqual relation, and at time t', the resonant current irAnd an excitation current imTo obtain a resonant current i by solvingrSubstituting the amplitudes of the sine component and the cosine component into the expression id(t) obtaining an output current i of the LLC resonant converterdAnd (3) a waveform expression in a switching period of which the half resonant period belongs.
Generally, by the above technical solution conceived by the present invention, the following beneficial effects can be obtained:
(1) according to the method, the instantaneous current is acquired once and theoretical analysis is carried out, so that the real-time output current condition of each switching period under the high-frequency work of the LLC converter can be calculated in real time, the dynamic characteristic and the response speed of a control algorithm of the LLC converter are improved, and the LLC converter is beneficial to accurate control under the high-frequency work state.
(2) The invention can realize sampling of single instantaneous current and finish current detection only by a current sampling chip with sampling speed matched with LLC switching frequency, does not need to add a complex sampling circuit, and has lower hardware requirement and low cost.
Drawings
Fig. 1 is a schematic structural diagram of a conventional LLC resonant converter;
FIG. 2 shows a switching signal and a resonant current i of a conventional LLC resonant converterrExciting current imAnd an output current i at the end of the rectifier circuitdA waveform schematic diagram; wherein, (a) is a waveform schematic diagram of a switching signal of the LLC resonant converter, and (b) is a resonant current i of the LLC resonant converterrAnd an excitation current imIs (c) the output current i at the end of the rectifying circuit of the LLC resonant converterdA waveform schematic diagram;
fig. 3 is a schematic diagram of a current detection method of the LLC resonant converter provided in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
Before explaining the technical solution of the present invention in detail, the structure of the LLC resonant converter and its operation principle will be briefly described as follows.
Structure of LLC resonant converter as shown in fig. 1, the circuit structure of the LLC resonant converter includes: input filter capacitor CiFour switching tubes (Q)1Q2Q3Q4) Formed inverter bridge and resonant inductor LrResonant capacitor CrTransformer T, four diodes (D)1D2D3D4) Rectifier circuit and output filter of constitutionWave capacitor Co(ii) a At the end of the rectifying circuit (e.g. the sampling point S shown in fig. 1) is the output current i of the LLC resonant converterd。
One switching cycle of the LLC resonant converter having a duration ts＝2t2The resonant period of the LLC resonant converter is tr＝2t1In the following embodiments, the LLC resonant converters are all operated at ts＞trThe working interval of (2); wherein the resonance period trIs concretely calculated by
Figure BDA0002592637710000061
After the drive current is injected into the LLC resonant converter shown in fig. 1, the LLC resonant converter starts to operate, and in the operation process, the switching signal and the resonant current irExciting current imAnd an output current i at the end of the rectifier circuitdThe waveform diagram is shown in fig. 2.
As shown in fig. 2 (a), at t0At the moment, i.e. at the beginning of a switching cycle (beginning of the first half of the resonant cycle), the switching tube Q1、Q4Turn on due to resonant current i before turn onrLess than 0, Q1、Q4In reverse conducting freewheeling state, therefore Q1、Q4The voltage at both ends is in clamping state to make Q1、Q4At t0The time can be switched on at Zero Voltage (ZVS), and the resonant current irFlows through Q1、Q4，LrAnd CrStarting the resonance, the transformer is clamped by the secondary side, the exciting current imThe voltage direction of the secondary side of the transformer is positive and negative, and the current flows through a rectifier diode D1、D4To power the load.
As shown in FIG. 2 (b), t1At the moment, i.e. at the end of the first half of the resonant period, the resonant current irWith excitation current imEqual in size, so that the energy exchange between the primary and secondary sides of the transformer is interrupted, the current on the secondary side rapidly drops to 0, and then the rectifier diode D1、D4Realize zero current turn-off and secondary side current io0. The clamp on the primary side of the transformer is eliminated due to the turn-off of the rectifying circuit, and the excitation inductance L of the transformer is eliminated at the momentmAnd a resonant inductor LrAnd a resonant capacitor CrResonance is generated due to the transformer excitation inductance LmMuch larger than the resonant inductance LrAnd thus the angular velocity ω of the three resonancesrMuch less than t0-t1The resonant angular velocity of the time segment, and thus the resonant current i at that timerWith excitation current imApproximately constant.
The invention provides a current detection method and a device of an LLC resonant converter, aiming at the problem that the current detection method of the existing LLC resonant converter cannot realize accurate and real-time detection of the current of a high-frequency LLC resonant converter because multiple times of sampling are needed and the current waveform of each switching period is estimated based on the sampling result.
Based on the above thought, the working principle of the LLC resonant converter is derived as follows:
by uCAnd uLRespectively representing resonant capacitances CrAnd a resonant inductor LrVoltage of (2) with I1,iniAnd V1,iniRepresents t0Resonance current i at timerAnd voltage uCAt an initial value of (i.e.
Figure BDA0002592637710000071
Because of the fact that
Figure BDA0002592637710000072
To obtain
Figure BDA0002592637710000073
Exciting current
Figure BDA0002592637710000081
Wherein, ViRepresenting the input voltage, V, of the LLC resonant converteroThe output voltage of the LLC resonant converter is shown, and N represents the turn ratio of a primary side and a secondary side of the transformer T;
due to the fact that at t0-t1In the time period, the resonant current irWith excitation current imApproximately constant, from which it can be seen that at t0-t1In time period im(t)＝ir(t)＝im(t1)＝ir(t1) And as shown in FIG. 2 (b), t3-t4Each waveform change and t within a time period (i.e., within the second half of the resonant period)0-t1The time segments being of equal size but opposite direction, i.e. im(t3)＝ir(t3)＝im(t0)＝ir(t0)＝-I1,iniI.e. by
Figure BDA0002592637710000082
Based on the above analysis, it can be calculated at t0-t1In time period, exciting current
Figure BDA0002592637710000083
From this expression, at t0-t1The exciting current is only related to known parameters of the structure parameter and the output voltage of the LLC resonant converter during the time period;
is provided with
Figure BDA0002592637710000084
The output current of LLC resonant converter is id(t)＝N|ir(t)-im(t) |, since t0The moment resonance current is equal to the excitation current, so ir(t0)＝im(t0) (ii) a At t0-t1Any time t' in the time period is opposite to the output current id(t) carrying outSampling to obtain a sampling current value i at the time td(t′)＝N|ir(t′)-im(t′)|；
Two-way simultaneous calculation
Figure BDA0002592637710000085
Two variables inr1And Ir2From which i can be calculatedd(t) the waveform expression during this switching period, deriving the instantaneous load of the LLC resonant converter during this period.
t3-t4In the time period (i.e. in the second half of the resonance period), the excitation current im(t) and a resonance current ir(t) waveform change and t0-t1The time periods are equal in size and opposite in direction, as shown in (c) of FIG. 2, t3-t4Within a time period, output current id(t) waveform change and t0-t1The time period is the same, therefore, at t3-t4Within a time period
Figure BDA0002592637710000086
id(t)＝N|ir(t)-im(t) |; likewise, at t3Time, ir(t3)＝im(t3) At t3-t4Any time t' in the time period is opposite to the output current id(t) sampling to obtain a sampling current value i at the time of td(t′)＝N|ir(t′)-im(t') |; the two formulas are combined to calculate two variables Ir1And Ir2From which i can be calculatedd(t) waveform representation over this switching period.
The following are examples.
The first embodiment is as follows:
a current detection method of an LLC resonant converter, as shown in fig. 3, includes:
converting the resonant current i of an LLC resonant converterrDecomposing the output current i of the LLC resonant converter into a form of superposition of a sine component and a cosine componentdArranged as resonant current i of LLC resonant converterrAnd an excitation current imIs expressed by the expression id(t)；
During the operation of the LLC resonant converter, the output current i is optionally adjusted at a time t' within one half resonant perioddSampling for one time to obtain a sampling current value id(t'), thereby obtaining a resonance current i at time trAnd an excitation current imThe relationship of (1);
at the beginning of a half resonance period in parallel, the resonance current irAnd an excitation current imEqual relation, and at time t', the resonant current irAnd an excitation current imTo obtain a resonant current i by solvingrSubstituting the amplitudes of the sine component and the cosine component into the expression id(t) obtaining an output current i at the end of the rectifying circuit in the LLC resonant converterdA waveform expression in a switching period to which a half of a resonance period belongs;
in the present embodiment, the half resonance period for sampling the output current is the first half resonance period within one switching period, i.e., t shown in fig. 20-t1In the time period, a current sampling point is the tail end of a rectifying circuit of the LLC resonant converter, namely a current sampling point S in the graph 1;
in the present embodiment, the first and second electrodes are,
Figure BDA0002592637710000091
combined stand
Figure BDA0002592637710000101
Solving to obtain a resonant current irOf the sine component and the cosine component of (a)r1And Ir2Substituting the expression id(t), obtaining a waveform expression of the output current of the LLC resonant converter in a switching period as
Figure BDA0002592637710000102
The instantaneous load of the LLC resonant converter in a switching period can be deduced on the basis of the waveform expression of the output current of the LLC resonant converter in the switching period;
as an optional implementation manner, this embodiment further includes:
according to the output current i at the tail end of a rectifying circuit in the LLC resonant converterdCalculating the output current i according to the waveform expression in the switching period of the half resonant perioddPeak and/or significant values within the corresponding switching period.
Generally speaking, according to the embodiment, by acquiring instantaneous current once and performing theoretical analysis, the real-time output current condition of each switching period under the high-frequency work of the LLC converter can be calculated in real time, the dynamic characteristic and the response speed of the LLC converter control algorithm are improved, and the LLC converter can be accurately controlled under the high-frequency work state.
Example two:
a current detection method for an LLC resonant converter is similar to the previous embodiments, except that in this embodiment, the half resonant period for sampling the output current is the second half resonant period within one switching period, i.e. t shown in fig. 23-t4A time period;
in the present embodiment, the first and second electrodes are,
Figure BDA0002592637710000111
combined stand
Figure BDA0002592637710000112
Solving to obtain a resonant current irOf the sine component and the cosine component of (a)r1And Ir2Substituting the expression id(t), obtaining a waveform expression of the output current of the LLC resonant converter in a switching period as
Figure BDA0002592637710000113
The instantaneous load of the LLC resonant converter during a switching period can be derived based on the waveform representation of the output current of the LLC resonant converter during this period.
Example three:
a current detection apparatus of an LLC resonant converter, comprising: a sampling unit and a calculating unit;
a calculation unit for calculating the resonant current i of the LLC resonant converterrDecomposing the output current i of the LLC resonant converter into a form of superposition of a sine component and a cosine componentdArranged as resonant current i of LLC resonant converterrAnd an excitation current imIs expressed by the expression id(t)；
A sampling unit for selecting an optional time t' in a half resonance period to output current i during the operation of the LLC resonant converterdSampling for one time to obtain a sampling current value id(t'), thereby obtaining a resonance current i at time trAnd an excitation current imThe relationship of (1); the sampling unit can be a current sampling chip with sampling speed matched with switching frequency;
a calculation unit for simultaneously calculating the resonance current i at the start of a half resonance periodrAnd an excitation current imEqual relation, and at time t', the resonant current irAnd an excitation current imTo obtain a resonant current i by solvingrSubstituting the amplitudes of the sine component and the cosine component into the expression id(t) obtaining an output current i at the end of the rectifying circuit in the LLC resonant converterdA waveform expression in a switching period to which a half of a resonance period belongs;
in this embodiment, please refer to the description of the method embodiments above for the specific implementation of each module, which will not be repeated here.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. A current detection method of an LLC resonant converter is characterized by comprising the following steps:
converting the resonant current i of the LLC resonant converterrDecomposing the output current i of the LLC resonant converter into a form of superposition of a sine component and a cosine componentdArranged as resonant current i of the LLC resonant converterrAnd an excitation current imIs expressed by the expression id(t); during the operation of the LLC resonant converter, optionally selecting a time t' within a half resonant period for the output current idSampling for one time to obtain a sampling current value id(t'), thereby obtaining said resonant current i at said time trAnd the exciting current imThe relationship of (1);
the resonance current i is simultaneously at the beginning of the half resonance periodrAnd the exciting current imEqual relation, and at said time t', said resonant current irAnd the exciting current imIs solved to obtain the resonance current irSubstituting the amplitudes of the sine component and the cosine component into the expression id(t) obtaining an output current i of the LLC resonant converterdAnd the waveform expression in the switching period of the half resonant period.
2. The method for detecting current of LLC resonant converter according to claim 1, characterized in that the output current of LLC resonant converter idArranged as resonant current i of the LLC resonant converterrAnd an excitation current imIs expressed by the expression idAfter (t), the expression id(t) is:
id(t)＝N|ir(t)-im(t)|
wherein N represents the turn ratio of the primary side and the secondary side of the transformer in the LLC resonant converter, and t represents a time variable.
3. Method for current detection of an LLC resonant converter as claimed in claim 1 or 2, characterized in that for said output current idThe half resonant period of sampling is the first half resonant period within one switching period.
4. A current detection method for an LLC resonant converter as claimed in claim 3, characterized in that the resonant current i of said LLC resonant converter is measuredrAfter being decomposed into a form of superposition of sine component and cosine component, the resonant current irThe expression of (a) is:
Figure FDA0002592637700000021
wherein, Ir1And Ir2Respectively representing the amplitudes, t, of the sine and cosine components of the resonance current after decompositionrRepresenting the resonance period of said LLC resonant converter, t representing a time variable.
5. A current detection method for an LLC resonant converter as claimed in claim 3, characterized in that the exciting current i of said LLC resonant convertermThe expression of (a) is:
Figure FDA0002592637700000022
wherein N represents a turn ratio of a primary side to a secondary side of a transformer in the LLC resonant converter, VoRepresenting the output voltage, t, of the LLC resonant converterrRepresenting the resonance period, L, of said LLC resonant convertermAnd the transformer excitation inductance in the LLC resonant transformation is represented, and t represents a time variable.
6. Method for current detection of an LLC resonant converter as claimed in claim 1 or 2, characterized in that for said output current idThe half resonant period of sampling is within one switching periodThe second half of the resonance period.
7. The method for detecting current of LLC resonant converter according to claim 6, characterized in that the resonant current of LLC resonant converter irAfter being decomposed into a form of superposition of sine component and cosine component, the resonant current irThe expression of (a) is:
Figure FDA0002592637700000023
wherein, Ir1And Ir2Respectively representing the amplitudes, t, of the sine and cosine components of the resonance current after decompositionrRepresenting the resonance period of said LLC resonant converter, t representing a time variable.
8. The method for detecting current of LLC resonant converter as claimed in claim 6, characterized in that exciting current i of LLC resonant convertermThe expression of (a) is:
Figure FDA0002592637700000024
wherein N represents a turn ratio of a primary side to a secondary side of a transformer in the LLC resonant converter, VoRepresenting the output voltage, t, of the LLC resonant converterrRepresenting the resonance period, L, of said LLC resonant convertermAnd the transformer excitation inductance in the LLC resonant transformation is represented, and t represents a time variable.
9. The method for detecting current of an LLC resonant converter as claimed in claim 1 or 2, further comprising:
the output current i of the LLC resonant converterdCalculating the output current i in the waveform expression of the switching period of the half resonant perioddPeak and/or significant values within the corresponding switching period.
10. A current detection device of an LLC resonant converter, characterized by comprising: a sampling unit and a calculating unit;
the computing unit is used for converting the resonant current i of the LLC resonant converterrDecomposing the output current i of the LLC resonant converter into a form of superposition of a sine component and a cosine componentdArranged as resonant current i of the LLC resonant converterrAnd an excitation current imIs expressed by the expression id(t)；
The sampling unit is used for selecting a time t' within a half resonant period to output the output current i in the process of operating the LLC resonant converterdSampling for one time to obtain a sampling current value id(t'), thereby obtaining said resonant current i at said time trAnd the exciting current imThe relationship of (1);
the computing unit is further configured to simultaneously determine the resonant current i at the start time of the half resonant periodrAnd the exciting current imEqual relation, and at said time t', said resonant current irAnd the exciting current imIs solved to obtain the resonance current irSubstituting the amplitudes of the sine component and the cosine component into the expression id(t) obtaining an output current i of the LLC resonant converterdAnd the waveform expression in the switching period of the half resonant period.
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